I think there will be other arrangements with UM. I found something a couple of weeks ago, drafted this, and then forgot to post it:
I suspect that other UM SIMs are going to have the data fairly soon
http://www.connect.de/news/TouristMo...ng_844956.html
The tariff and other details are so similar it's unlikely to be a coincidence. The current Tourist Mobile SIM is Vistream-based, but it seems they will be launching another product
http://www.tourist-mobile.com/web/travel_sim_pro.html